JP2000233761A - Steering control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the turning performance of a vehicle by carrying out a necessary correcting steering while preventing the unnecessary correcting steering, thereby making the slip angle of a steering wheel adequate, and preventing the reduction of the lateral force of the steering wheel adequately. SOLUTION: The slip angles αf1 to αf3 of front wheels are inferred by observers 1 to 3 depending on vehicle models different each other respectively (S20 to 40), and when the marks of the inferred slip angles αf1 to αf3 are the same, the smallest value of them is set to the inferred slip angle αf, and when the marks of them are different, the inferred slip angle αf is set 0 (S50 to 80). In this case, a correcting steering device 24 is controlled depending on the correcting angle θa responding to the inferred slip angle αf of the front wheels, and thereby, the left and right side front wheels are correcting steered by the correcting steering angle θa (S130 and 140).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering control device for a vehicle, and more particularly, to a steering control device for improving turning performance of a vehicle by performing corrective steering, that is, intervention steering for driver's steering.

[0002]

2. Description of the Related Art As one of steering control devices for vehicles such as automobiles, for example, Japanese Patent Application Laid-Open No. Hei 5-31 filed by the present applicant.
As described in Japanese Patent No. 9289, when the cornering force and the slip angle of the steered wheels are estimated based on the state quantity of the vehicle and the operation amount of the driver, and the value obtained by partially differentiating the cornering force with the slip angle is negative. 2. Description of the Related Art There has been conventionally known a steering control device configured to perform correction steering using a deviation between a slip angle and a preset limit slip angle as a correction steering angle.

According to such a steering control device, if the steering angle is excessively increased by the driver, the slip angle of the steered wheels becomes excessive, and the value obtained by partially differentiating the cornering force with the slip angle becomes negative. For example, when there is a high possibility that the lateral force of the steered wheels is reduced due to excessive steering, the corrected steering is performed by using the deviation between the slip angle and the preset limit slip angle as the corrected steering angle to perform steering of the steered wheels. Since the actual steering angle is reduced, it is possible to appropriately prevent the lateral force of the steered wheels from being reduced due to excessive steering, thereby improving the turning performance of the vehicle.

[0004]

However, in the steering control device according to the prior proposal described in the above publication,
Since both the cornering force and the slip angle are estimated values, a value obtained by partially differentiating the cornering force with the slip angle is a sensor for detecting the state quantity of the vehicle and the driver's operation amount for estimating the cornering force and the slip angle. It may not be possible to accurately determine whether there is a high possibility that the lateral force of the steered wheels will be reduced due to excessive steering due to excessive detection errors. There is a problem that steering is performed or necessary correction steering is not performed.

The present invention has been made in view of the above-mentioned problem in a conventional steering control device configured to perform correction steering when a value obtained by partially differentiating a cornering force with respect to a slip angle is negative. A main object of the present invention is to perform the necessary corrective steering while preventing unnecessary corrective steering by performing corrective steering according to the slip angle so that the slip angle decreases when the slip angle of the steered wheels is excessive. The purpose of this is to improve the turning performance of the vehicle by optimizing the slip angle of the steered wheels, preventing the lateral force of the steered wheels from lowering.

[0006]

SUMMARY OF THE INVENTION According to the present invention, there is provided a motor vehicle comprising: a slip angle detecting means for detecting a slip angle of a steering wheel; Correction steering angle calculating means for calculating a corrected steering angle of the steered wheels for reduction in accordance with the slip angle detected by the slip angle detecting means, and correcting steering for correcting the steered wheels based on the corrected steering angle. Means for controlling the steering of a vehicle.

According to the first aspect of the present invention, the slip angle of the steered wheel is detected, and the corrected steering angle of the steered wheel for reducing the slip angle of the steered wheel is set to the slip angle detected by the slip angle detecting means. The steered wheel is corrected based on the corrected steering angle, so that even if the driver performs excessive steering and the slip angle of the steered wheel becomes excessive, the slip angle of the steered wheel is reduced by the corrected steering. As a result, a reduction in the lateral force of the steered wheels is reliably prevented.

According to the present invention, in order to effectively achieve the above-mentioned main object, in the above-mentioned construction, the slip angle detecting means may be different from each other in vehicle models having at least a steering angle as a parameter. A plurality of slip angle estimating means for estimating the slip angle of the steered wheels based on the plurality of slip angle estimation values, and a slip angle estimation value having the smallest magnitude among the plurality of slip angle estimation values estimated by the plurality of slip angle estimation means is detected. And a slip angle determining means for determining the slip angle.

According to the configuration of the second aspect, the slip angles of the steered wheels are estimated by the plurality of slip angle estimating means based on different vehicle models using at least the steering angle as a parameter, and are estimated by the plurality of slip angle estimating means. Since the slip angle estimated value having the smallest magnitude among the plurality of slip angle estimated values obtained is determined as the detected slip angle, the steered wheels may be unnecessarily corrected and steered at an excessively corrected steering angle. It is surely prevented.

[0010]

According to a preferred aspect of the present invention, in the configuration of the first aspect, when the magnitude of the detected slip angle is equal to or larger than a reference value, (Preferred mode 1).

According to another preferred embodiment of the present invention, in the configuration of claim 2, the slip angle determining means includes a plurality of slip angles when the estimated slip angle estimated values have the same sign. The slip angle estimation value having the smallest magnitude among the angle estimation values is determined to be the detected slip angle, and the slip angle is determined to be 0 when the signs of the plurality of estimated slip angle estimation values are not the same. (Preferred embodiment 2).

According to still another preferred aspect of the present invention, in the configuration of claim 2, the plurality of slip angle estimating means are configured to be different observers using at least the steering angle as an input parameter. (Preferred embodiment 3).

According to still another preferred aspect of the present invention, in the configuration of the first aspect, the steering control device includes a yaw rate detecting means for detecting an actual yaw rate of the vehicle, and the slip angle detecting means includes at least a slip angle detecting means. A plurality of observers for estimating the slip angle of the steered wheels and the yaw rate of the vehicle based on different vehicle models each having the steering angle as a parameter, and the magnitude of the deviation between the actual yaw rate detected by the yaw rate detection means and the estimated yaw rate are determined. And a slip angle determining means for determining the slip angle estimated value estimated by the smallest observer as the detected slip angle (preferred mode 4).

According to still another preferred aspect of the present invention, in the configuration of the first aspect, the steering control device includes a yaw rate detecting means for detecting an actual yaw rate of the vehicle, and the slip angle detecting means includes at least a slip angle detecting means. A plurality of observers for estimating the slip angle of the steered wheels and the yaw rate of the vehicle based on different vehicle models using the steering angle as a parameter, and means for calculating a deviation between the actual yaw rate detected by the yaw rate detection means and the estimated yaw rate When,
Means for calculating a weight for each slip angle estimated value such that the larger the deviation of the yaw rate is, the smaller the weighted average value of the slip angle estimated value is calculated based on the calculated weight, and the average value is detected. And a slip angle determining means for determining the slip angle (preferred mode 5).

According to still another preferred aspect of the present invention, in the configuration of the first aspect, the vehicle has a steering torque assist type steering device, and the steering control device includes a steering torque detecting means, Means for calculating an assist torque according to the detected steering torque; correction torque calculating means for calculating a correction torque at least according to the corrected steering angle; and a steering torque of the steering device using the assist torque corrected by the correction torque. (Preferred mode 6).

According to still another preferred embodiment of the present invention, in the configuration of the above-mentioned preferred embodiment 6, the correction torque calculating means calculates a first correction torque based on the correction steering angle, and calculates a correction steering angle. The second correction torque is calculated based on the change rate, and the correction torque is calculated as the sum of the first correction torque and the second correction torque (preferred mode 7).

According to still another preferred aspect of the present invention, in the configuration of the preferred aspect 6, the steering control device includes a yaw rate detecting means for detecting an actual yaw rate of the vehicle, and the correction torque calculating means includes at least a correcting torque calculating means. The target yaw rate of the vehicle is calculated based on the steering angle, the deviation between the actual yaw rate and the target yaw rate is calculated, and the magnitude decreases as the magnitude of the product increases based on the product of the absolute value of the deviation and the corrected steering angle. It is configured to calculate the first correction torque so as to be as follows (preferred mode 8).

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail with reference to the accompanying drawings, in which several preferred embodiments are shown.

FIG. 1 is a schematic configuration diagram showing a first preferred embodiment of a vehicle steering control device according to the present invention applied to a vehicle provided with an electric power steering device.

In FIG. 1, 10FL and 10FR denote left and right front wheels of the vehicle 12, respectively, and 10RL and 10RR denote left and right rear wheels which are driving wheels of the vehicle, respectively. The left and right front wheels 10FL and 10FR, which are both driven wheels and steering wheels, are tie rods 18L and 1F by a rack-and-pinion type electric power steering device 16 driven in response to the steering of the steering wheel 14 by the driver.
Steered via 8R.

In particular, in the illustrated embodiment, the power steering device 16 is a power steering device of a steering torque assist type, and an upper shaft 20 and a lower shaft connecting the steering wheel 14 and a gear box of the power steering device 16. A correction steering device 24 is interposed between the correction steering device 22 and the steering wheel 22. The correction steering device 24 includes, for example, a motor and a gear mechanism, and performs the correction steering by rotating the lower shaft 22 relatively to the upper shaft 20.

The power steering device 16 and the correction steering device 24 generate an assist torque for reducing the driver's steering load, as will be described in detail later, and correct the reduction of the front wheel lateral force caused by the driver's excessive steering. Is controlled by the electric control device 26 so as to prevent the occurrence of the electric shock. The power steering device 16 is controlled by the electric control device 26 to generate a corrected assist torque according to the corrected steering when the corrected steering is performed to correct the fluctuation of the steering reaction force caused by the corrected steering.

As shown in the figure, a signal indicating a steering angle θ detected by a steering angle sensor 28 provided on the upper shaft 20 and an actual yaw rate γ of the vehicle detected by a yaw rate sensor 30 are provided to an electric control device 26. A signal, a signal indicating the vehicle speed V detected by the vehicle speed sensor 32, and a signal indicating the steering torque Ts detected by the torque sensor 34 are input.

The steering angle sensor 28 and the like detect the steering angle θ and the like with the value in the case of a left turn of the vehicle as positive. Although not shown in detail in FIG. 1, the electric control device 26 has, for example, a CPU, a ROM, a RAM, and an input / output port device.
These may include a microcomputer having a general configuration and a drive circuit connected to each other by a bidirectional common bus.

The electric control device 26 calculates estimated slip angles αf1 to αf3 of the front wheels by observers 1 to 3 using the steering angle θ and the vehicle speed V as input parameters according to a flowchart shown in FIG. Estimated slip angle αf1
When the signs of .about..alpha.f3 are the same, the magnitude of the magnitude is assumed to be the smallest value, and the estimated slip angles .alpha.f1 to .alpha.f3
Are different, the estimated slip angle αf of the front wheels is calculated as 0, the corrected steering angle θa of the front wheels is calculated based on the estimated slip angle αf, and the corrected steering device 24 is controlled based on the corrected steering angle θa. Steering reduces the slip angle of the front wheels.

The electric control device 26 calculates a basic assist torque Tb based on the steering torque Ts detected by the torque sensor 34 in accordance with a routine shown in FIG. The first correction torque Ta1 is calculated, the second correction torque Ta2 is calculated based on the differential value θad of the correction steering angle, and the basic assist torque Tb is corrected by the first correction torque Ta1 and the second correction torque Ta2. A later assist torque Tas is calculated, and the assist control of the steering torque is performed by controlling the electric power steering device 16 based on the assist torque Tas.

Next, the correction steering control in the first embodiment will be described with reference to the flowchart shown in FIG. The correction steering control according to the flowchart shown in FIG. 2 is started by closing an ignition switch (not shown), and is repeatedly executed at predetermined time intervals.

First, at step 10, a signal indicating the steering angle θ detected by the steering angle sensor 28 is read, and at step 20, the actual steering angle δ of the front wheels is calculated based on the steering angle θ. And the following equations 1 to 5 and FIG.
The estimated slip angle αf of the front wheel, the estimated slip angle αr of the rear wheel, the lateral force Ff of the front wheel, the lateral force Fr of the rear wheel, the slip angle β of the vehicle are obtained from the map corresponding to the graph shown by the solid line in FIG. The vehicle yaw rate γh and the vehicle lateral speed Vy are estimated, the estimated front wheel slip angle αf is set to the estimated slip angle αf1 by the observer 1, and the estimated vehicle yaw rate γh is estimated by the observer 1. Set to γh1.

Αf = −β + δ−Lf · γh / Vx (1) αr = −β + Lr · γh / Vx (2) γd = (Lf · Ff−Lr · Ff) / Iz (3) Vyd = (Ff + Fr) / m−Vx · γh (4) β = Vy / Vx (5)

In the above equations, Lf and Lr are the distances between the center of gravity of the vehicle and the front and rear axles, respectively, Vx is the longitudinal speed of the vehicle (= vehicle speed V), and Iz is The yaw moment of inertia of the vehicle, m is the weight of the vehicle, γd is the differential value of the yaw rate γ of the vehicle, and Vyd is the differential value of the lateral speed Vy of the vehicle. Equations 3 and 4 above
Is a differential equation, the solution is calculated by the difference.
Further, the graphs shown in FIGS. 4 and 5 are set based on vehicle models having different road surface friction coefficients, for example.

In step 30, the estimated slip angle αf of the front wheel, the estimated slip angle αr of the rear wheel, and the maps corresponding to the above equations 1 to 5 and the graphs indicated by broken lines in FIGS. Vehicle slip angle β, vehicle yaw rate γ
h, the lateral speed Vy of the vehicle is estimated, the estimated front wheel slip angle αf is set to the estimated slip angle αf2 by the observer 2, and the estimated vehicle yaw rate γh is set to the estimated yaw rate γh2 by the observer 2. You.

In step 40, the estimated slip angle αf of the front wheel and the estimated slip angle αr of the rear wheel are obtained from the above equations 1 to 5 and the maps corresponding to the graphs indicated by the dashed lines in FIGS. , The vehicle's slip angle β, the vehicle's yaw rate γh, and the vehicle's lateral velocity Vy are estimated, and the estimated slip angle αf of the front wheels is estimated by the observer 3.
Set to 3 and the estimated vehicle yaw rate γh
Is set to the yaw rate γh3 estimated by the observer 3.

In step 50, observers 1 to 3
Front wheel slip angle αfj (j = 1, 2,
It is determined whether or not all of 3) have the same sign. If a negative determination is made, the estimated slip angle αf of the front wheels is set to 0 in step 60, and an affirmative determination is made. Sometimes the process proceeds to step 70.

In step 70, the minimum value αfamin of the absolute value of the estimated slip angle αfj is calculated in accordance with the following equation 6 by taking min ｛{｛} as the minimum value among the numerical values in {｝}. The estimated slip angle αf of the front wheel is calculated according to the following equation 7 using signαf1 as the sign of the estimated slip angle αf1. αfamin = min ｛| αf1 |, | αf2 |, | αf3 |｝ (6) αf = signαf1 · αfamin (7)

In step 130, based on the estimated slip angle αf of the front wheel, a corrected steering angle θa of the front wheel is calculated from a map corresponding to the graph shown in FIG.
In 40, the corrective steering device 24 is controlled based on the corrective steering angle θa of the front wheels, whereby the left and right front wheels 10FL and 1FL are controlled.
0FR is corrected and steered at the corrected steering angle θa.

Next, the steering torque assist control in the first embodiment will be described with reference to the flowchart shown in FIG. Note that the assist control according to the flowchart shown in FIG. 3 is also started by closing an ignition switch (not shown) and is repeatedly executed at predetermined time intervals.

First, in step 210, a signal indicating the steering angle θ detected by the steering angle sensor 28 is read, and in step 220, the torque sensor 3 is read.
4 based on the steering torque Ts detected from the map shown in FIG.
b is calculated.

In step 230, the actual steering angle δ of the front wheels is calculated based on the steering angle θ, and the target yaw rate γt of the vehicle is calculated according to the following equation 8 using H as the wheel base of the vehicle and Kh as the stability factor. Is calculated, and the deviation γ−γt between the target yaw rate γt and the actual yaw rate γ of the vehicle detected by the yaw rate sensor 30 is calculated.
Is calculated as the yaw rate deviation Δγt. γt = V · δ / (1 + Kh · V ² ) H (8)

In step 240, based on the product of the absolute value of the yaw rate deviation Δγt and the corrected steering angle θa calculated in step 130 in FIG. 2, a first map is obtained from a map corresponding to the graph shown in FIG. Is calculated.

In step 250, a differential value θad of the corrected steering angle θa of the front wheels is calculated, and in step 260, based on the differential value θad of the corrected steering angle, a map corresponding to the graph shown in FIG. A second correction torque Ta2 is calculated.

In step 270, the correction torque Ta is calculated as the sum of the first correction torque Ta1 and the second correction torque Ta2 according to the following equation (9). Ta = Ta1 + Ta2 (9)

In step 280, the corrected assist torque Tas is calculated as the sum of the basic assist torque Tb calculated in step 220 and the correction torque Ta calculated in step 270 according to the following equation (10). In step 290, the assist torque Tas
The electric power steering device 16 is controlled on the basis of the above, the assist control of the steering torque is executed, and then the process returns to step 210. Tas = Tb + Ta (10)

FIGS. 10 and 11 are flowcharts showing the steering control routine in the second and third embodiments of the vehicle steering control device according to the present invention, respectively. FIG. 1
Steps 0 and the same steps as those shown in FIG. 2 are given the same step numbers as those shown in FIG. In these embodiments, although not shown, steering torque assist control similar to the steering torque assist control in the first embodiment is performed.

In the second embodiment shown in FIG. 10, in step 90 executed after step 40, the deviation Δγj between the actual yaw rate γ and the estimated yaw rate γhj is calculated according to the following equation (11). Is done. Δγj = γ−γhj (11)

In step 100, based on the absolute value of the deviation Δγj of the yaw rate, the estimated slip angles αfj respectively corresponding to the maps corresponding to the graph shown in FIG.
Are calculated. (J = 1, 2, 3).

In step 110, the estimated slip angle αf of the front wheels is calculated as a weighted average value of the estimated slip angle αfj according to the following equation 12. Note that in FIG. 10, the following equation 12 is shown in simplified notation. αf = (W1 · αf1 + W2 · αf2 + W3 · αf3) / (W1 + W2 + W3) (12)

Further, in the third embodiment shown in FIG. 11, the yaw rate deviation Δ
γj is calculated, and thereafter, in step 120, the deviation of the yaw rate having the minimum absolute value among the deviations of the yaw rate Δγj is specified, and the slip of the front wheels estimated by the observer corresponding to the specified yaw rate deviation is calculated. The angle αfj is determined as the estimated slip angle αf of the front wheel.

Thus, according to the above embodiments, the slip angles αf1 to αf3 of the front wheels by the observers 1 to 3 are estimated in steps 20 to 40, respectively, and in the first embodiment, the steps 50 to 80 are performed. Thus, the optimum value of the front wheel slip angles αf1 to αf3 is changed to the estimated slip angle αf by steps 90 to 110 in the second embodiment and by steps 90 and 120 in the third embodiment. The corrected steering device 24 is set on the basis of the corrected steering angle θa corresponding to the estimated slip angle αf of the front wheels in steps 130 and 140, whereby the left and right front wheels 10 are controlled.
FL and 10FR are corrected and steered at the corrected steering angle θa.

Accordingly, since the actual steering angles of the left and right front wheels 10FL and 10FR are reduced by an amount corresponding to the corrected steering angle θa, and thereby the slip angle of the front wheels is reduced, even if the driver performs excessive steering, It is possible to reliably prevent the lateral force of the front wheels from being reduced due to the excessively large slip angle of the front wheels and to deteriorate the steering stability during turning of the vehicle, thereby improving the turning performance of the vehicle.

For example, as shown in FIG. 13, in a conventional general vehicle in which correction steering is not performed, the actual slip angle αfa of the front wheels is limited due to excessive steering performed by the driver. If the slip angle αfo becomes too large (see FIG. 15), the actual lateral force Ffa of the front wheels 10FL and 10FR decreases, and the vehicle tends to drift out.

On the other hand, according to each of the above-described embodiments, as shown in FIG. 14, the actual steering angles of the front wheels 10FL and 10FR are reduced by an amount Δδ corresponding to the corrected steering angle θa, so that the actual front wheels are reduced. Is reduced so that the slip angle αfa does not substantially exceed the limit slip angle αfo, it is possible to prevent a reduction in the actual lateral force Ffa of the front wheels, thereby preventing the vehicle from drifting out. As a result, the stability of the vehicle when turning can be improved.

In particular, according to the first embodiment, step 7
Since the smallest value among the slip angles αf1 to αf3 of the front wheels estimated by the observers 1 to 0 at 0 and 80 is set as the estimated slip angle αf, the corrected steering angle θa becomes excessive. Can be reliably prevented,
As a result, it is possible to reliably prevent the unnecessary excessive correction steering from being performed, and to prevent the stability at the time of turning of the vehicle from being deteriorated and the driver from feeling uncomfortable. .

When the estimated slip angle αf of the front wheels is set to the smallest value among the estimated slip angles αf1 to αf3 regardless of whether the signs of the estimated slip angles αf1 to αf3 are the same or not. As shown in FIG. 16, the estimated slip angle αf of the front wheel sharply changes in a saw-tooth shape in a region where the signs of the estimated slip angles αf1 to αf3 are different from each other. θa may also change irregularly and abruptly, and in such a situation, the stability of the vehicle may be degraded or the occupant of the vehicle may feel uncomfortable.

On the other hand, according to the first embodiment described above, the estimated slip angles αf of the front wheels are larger when the signs of the estimated slip angles αf1 to αf3 are the same in steps 50 to 80. Set to the lowest value,
When the signs of the estimated slip angles αf1 to αf3 are different, they are set to 0. Therefore, as shown in FIG. 17, in the region where the signs of the estimated slip angles αf1 to αf3 are different, the estimated slip angle αf of the front wheel and the front wheel It is possible to reliably prevent the corrected steering angle θa from suddenly changing like a saw blade, thereby deteriorating the stability of the vehicle or the occupant of the vehicle in the situation where the signs of the estimated slip angles αf1 to αf3 are different. Can be surely prevented from feeling uncomfortable.

According to the second embodiment, in steps 90 to 110, the smaller the deviation Δγj between the actual yaw rate γ and the estimated yaw rate γhj, the larger the weight Wj for the estimated slip angle αfj is. Since the estimated slip angle αf of the front wheels is calculated as the weighted average value of the estimated slip angle αfj, the weighted average value obtained by increasing the weight Wj with respect to the estimated slip angle αfj estimated by the observer with high estimation accuracy is estimated. The slip angle αf can be calculated with high accuracy.

According to the third embodiment, the slip angle αfj of the front wheel estimated by the observer corresponding to the yaw rate deviation having the smallest absolute value of the yaw rate deviation Δγj is equal to the estimated slip angle of the front wheel. Since it is determined as αf, the estimated slip angle αf of the front wheels can be calculated with high accuracy as a value close to the actual value.

Therefore, according to the second and third embodiments described above, the front wheels can be corrected and steered at the corrected steering angle θa based on a value close to the actual slip angle αfa of the front wheels. The front wheels can be corrected and steered accurately without excess or deficiency regardless of the condition of the vehicle such as the coefficient.

In any of the first to third embodiments, the basic assist torque Tb is calculated in step 220 based on the steering torque Ts.
At 30 and 240, a deviation Δγt between the target yaw rate γt of the vehicle and the actual yaw rate γ is calculated, and a first correction torque Ta1 is calculated based on the product of the absolute value of the yaw rate deviation Δγt and the correction steering angle θa. In steps 250 and 260, a second correction torque Ta2 is calculated based on the differential value θad of the correction steering angle, and steps 270 to 29 are performed.
At 0, the assist control of the steering torque is performed based on the assist torque Tas after the basic assist torque Tb is corrected by the first correction torque Ta1 and the second correction torque Ta2.

Therefore, according to each of the above-described embodiments, not only the left and right front wheels are corrected and steered at the corrected steering angle θa, but also
It is possible to reliably prevent the steering reaction force felt by the driver from unnaturally fluctuating due to the corrected steering, and thereby, when the basic assist torque is not corrected by the first and second correction torques. In comparison, the steering feeling can be improved.

In particular, in any of the above-described embodiments, as the magnitude of the correction steering angle θa of the front wheels increases, not only does the magnitude of the first correction torque Ta1 decrease, but also the absolute value of the yaw rate deviation Δγt decreases. Since the first correction torque is calculated so that the magnitude of the first correction torque decreases as the magnitude increases, the first correction torque is surely reduced during the limit traveling of the vehicle in which the magnitude of the yaw rate deviation is excessive, As a result, it is possible to reliably prevent the correction torque from becoming excessive in the limit traveling region of the vehicle and in the vicinity thereof.

In any of the above embodiments, the basic assist torque Tb is corrected not only by the first correction torque Ta1 but also by the second correction torque Ta2. Since the torque Ta2 is calculated so as to increase as the value of the differential value θad of the corrected steering angle θa of the front wheels increases, the variation in the steering reaction force generated due to friction inside the steering device during the corrected steering can be reliably determined. Can be offset.

Although the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments may be included within the scope of the present invention. It will be clear to those skilled in the art that is possible.

For example, in each of the above-described embodiments, the corrected steering angle θa of the front wheels is calculated based on the estimated slip angle αf of the front wheels, but the corrected steering angle θa of the front wheels is calculated. The control amount θa1 based on the slip angle αf is calculated as a linear sum of the control amount θa2 based on the deviation between the target yaw rate γt of the vehicle and the actual yaw rate γ, whereby the actual steering angle of the front wheels is feedback based on the slip angle of the front wheels. It may be modified to be controlled by both the control and the feedback control based on the yaw rate deviation.

In each of the above embodiments, the number of observers for estimating the front wheel slip angle αf is three, but the number of observers is set to an arbitrary number other than three as necessary. You may.

Further, in each of the above-described embodiments, in order to correct the fluctuation of the steering reaction force caused by the correction steering, step 2 is performed.
Although the steering torque assist control is performed according to 10 to 290, the steering torque assist control for correcting the fluctuation of the steering reaction force caused by the correction steering may be performed in an arbitrary mode. The torque assist control may be omitted.

In each of the above embodiments, only the front wheels are steered wheels, and correction steering is performed only on the front wheels. However, the present invention is applied to a vehicle having a four-wheel steering device. In such a case, the correction steering may be performed so as to perform the corrective steering for both the front wheels and the rear wheels.

Further, in each of the above-described embodiments, the front wheel steering device is a rack-and-pinion type electric power steering device 16, and the correction steering device 2
4 is a lower shaft 2 relative to the upper shaft 20
2, the corrective steering is performed by rotating the front wheel 2. However, the front wheel steering device and the corrective steering device may have any structure known in the art.

[0068]

As is apparent from the above description, according to the structure of the first aspect, even if the driver performs excessive steering and the slip angle of the steered wheels becomes excessive, the slip angle of the steered wheels becomes large. Since the correction steering reduces the slip angle in accordance with the slip angle, it is possible to reliably prevent the lateral force of the steered wheels from lowering, thereby improving the turning performance of the vehicle.

According to the first aspect of the present invention, the corrected steering angle is calculated according to the slip angle detected by the slip angle detecting means.
No. 89, as compared with a case where the necessity of the correction steering is determined based on whether or not a value obtained by partially differentiating the estimated cornering force at the estimated slip angle is negative. It is possible to reduce a possibility that unnecessary correction steering is performed or required correction steering is not performed due to an influence of a detection error of a sensor that detects a state amount of a vehicle or a driver's operation amount. it can.

According to the second aspect of the present invention, the slip angles of the steered wheels are estimated by the plurality of slip angle estimating means based on different vehicle models using at least the steering angle as a parameter, and are estimated by the plurality of slip angle estimating means. Since the slip angle estimated value having the smallest magnitude among the plurality of slip angle estimated values thus determined is determined as the detected slip angle, it is necessary to prevent the steered wheels from being unnecessarily corrected and steered at the excessive corrected steering angle. It can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a first preferred embodiment of a vehicle steering control device according to the present invention applied to a vehicle including an electric power steering device.

FIG. 2 is a flowchart illustrating a steering control routine according to the first embodiment.

FIG. 3 is a flowchart illustrating a steering torque assist control routine according to the first embodiment.

FIG. 4 is a graph showing a relationship between an estimated slip angle αf of the front wheels and a lateral force Ff of the front wheels.

FIG. 5 is a graph showing a relationship between an estimated slip angle αr of the rear wheel and a lateral force Fr of the rear wheel.

FIG. 6 is a graph showing a relationship between an estimated slip angle αf of the front wheels and a corrected steering angle θa of the front wheels.

FIG. 7 is a graph showing a relationship between a detected steering torque Ts and a basic assist torque Tb.

FIG. 8 is a graph showing a relationship between a product of an absolute value of a yaw rate deviation Δγt and a corrected steering angle θa of a front wheel and a first correction torque Ta1.

FIG. 9 is a graph showing a relationship between a differential value θad of a corrected steering angle θa of a front wheel and a second correction torque Ta2.

FIG. 10 is a flowchart showing a steering control routine in a second embodiment of the vehicle steering control device according to the present invention.

FIG. 11 is a flowchart showing a steering control routine in a third embodiment of the vehicle steering control device according to the present invention.

FIG. 12 shows the actual yaw rate γ and the estimated yaw rate γhj of the vehicle.
9 is a graph showing a relationship between an absolute value of a deviation Δγj from the weight and a weight Wj.

FIG. 13 is an explanatory diagram showing a case where excessive steering is performed by a driver in a conventional general vehicle in which correction steering is not performed.

FIG. 14 is an explanatory diagram showing an operation of each of the illustrated embodiments when an excessive steering is performed by a driver.

FIG. 15 is a graph showing an example of the relationship between the actual slip angle αfa of the front wheels and the actual lateral force Fa of the front wheels.

FIG. 16 is a graph showing an example in which the estimated slip angle αf of the front wheels is set to the smallest value among the estimated slip angles αf1 to αf3.

FIG. 17 shows an estimated slip angle αf1 in the first embodiment.
9 is a graph showing an example of a variation of an estimated slip angle αf with respect to? F3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 16 ... Electric power steering device 24 ... Correction steering device 26 ... Electric control device 28 ... Steering angle sensor 30 ... Yaw rate sensor 32 ... Vehicle speed sensor 34 ... Torque sensor

Claims (2)

[Claims] 1. A slip angle detecting means for detecting a slip angle of a steered wheel, and a corrected steering angle of the steered wheel for reducing the slip angle of the steered wheel is set to a slip angle detected by the slip angle detecting means. A steering control device for a vehicle, comprising: a corrected steering angle calculating means for calculating the corrected steering angle in accordance with the corrected steering angle; A plurality of slip angle estimating means for estimating a slip angle of the steered wheels based on different vehicle models using at least a steering angle as a parameter; and a plurality of slip angle estimating means. 2. A slip angle determining means for determining a slip angle estimated value having the smallest value among the plurality of estimated slip angle values as a detected slip angle.
A vehicle steering control device according to claim 1.